1947 16M Polarity ??

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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1947 16M Polarity ??

Postby Bentley9 » Sun Nov 04, 2018 4:25 pm

Hello,
I have a 1947 16M which doesn’t charge the battery. I plan to refurbish the dynamo and wiring and wondered if anyone could confirm whether this bike should be positive or negative earth ?
Many Thanks


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Re: 1947 16M Polarity ??

Postby SPRIDDLER » Sun Nov 04, 2018 5:11 pm

Welcome, Mark.
Neg Earth originally.
First check which terminal of your battery is earthed. It may have been changed by a PO to pos earth.

See wiring diagram on page 77 of the original Owners Manual here: (It's actually for a 'Matchless' but the same wiring)

http://archives.jampot.dk/book/Owners_m ... Manual.pdf

You can probably find a clearer copy (and much more) if you search the 'Books' section here:

http://archives.jampot.dk/

There's an excellent website covering testing our Ajay and Matchless Lucas dynamos/charging/circuits etc. here:

https://matchlessclueless.com/
I poke badgers with spoons.

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Re: 1947 16M Polarity ??

Postby Bentley9 » Sun Nov 04, 2018 6:15 pm

Thank you for the information and useful links.
The bike is currently wired Positive Earth so I think I’ll return to Negative as per the manual.
Do you know what the reason would have been for a PO to wire it Positive ?


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Re: 1947 16M Polarity ??

Postby SPRIDDLER » Sun Nov 04, 2018 6:28 pm

Bentley9 wrote:Do you know what the reason would have been for a PO to wire it Positive ?

It really doesn't matter whether you have pos or neg earth unless it's necessary to respect the polarity of some aftermarket accessories that need pos earth e.g. some LED lighting units, electronic voltage regulator etc.
However, if the battery/circuit polarity is changed it's essential to 'flash' the dynamo (all explained on the Matchless Clueless website) and alter the voltage regulator configuration, although this may not be possible on some electronic (solid state) regulators which may be suitable for one earth polarity ONLY.
EDIT;
It has just occurred to me that the reason yours isn't charging is that it should be (i.e. it previously was) neg earth and maybe 'someone' ;) has connected the battery incorrectly. This can damage an electronic regulator which has been set up for neg earth and the battery is connected with pos to earth (and vice-versa).

Is the bike new to you?
Has it ever charged o.k. or don't you know (because it's new to you)?

Another diagnostic question:
When you put the lights on (engine stopped) does the ammeter show a pos + or a neg - reading?
I poke badgers with spoons.

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